Feel Like You’ve Run a Marathon? Long COVID Study Suggests Why - Healthrising

Nice writeup by Cort Johnson on a recent long covid study:


An excerpt

The authors didn’t employ people with ME/CFS in the study but highlighted the “broad overlap” between the two diseases and referring to Wirth and Scheibenbogen’s ME/CFS hypothesis proposed that both feature problems with calcium dysregulation that in turn affects the adrenergic and muscarinic receptors that regulate blood flows.

Interresting theory.


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The blog tries to link the research to the currently popular "ischemia-reperfusion hypothesis", which proposes that PEM is caused by improper blood flow:

The study used a technique called “flow-mediated skin fluorescence (FMSF) which the authors stated was “uniquely suitable” for assessing the microcirculation during periods of low blood flow (transient ischemia). A recent hypothesis proposed that people with long COVID or ME/CFS were in a chronic state of transient ischemia due to inadequate blood flows.

Putting aside the fact that "chronic transient ischemia" is an oxymoron, the "ischemia-reperfusion hypothesis" is indeed a popular theory right now due to interest in the cardiovascular manifestations of a coronaviral infection. However, upon further inspection, this theory falls flat.

Specifically, the symptoms of PEM are nothing like the symptoms of ischemia-reperfusion injuries. Whereas PEM symptoms are generalized and varied, ischemia-reperfusion injuries tend to produce localized, well-defined symptoms.

For example, ischemia-reperfusion injuries in limbs can produce myalgia and paresthesias, which is something like Delayed-Onset Muscle Soreness (DOMS) with Peripheral Neuropathy (PN). Inflammation markers in such ischemia-reperfusion injuries would likely be elevated, whereas inflammation markers in PEM are not reliably elevated.

An ischemia-reperfusion injury to the brain would produce stroke-like symptoms, essentially a Transient Ischemic Attack (TIA). Although cognitive exertion can trigger PEM, it is not at all clear how cognitive exertion could produce a TIA.

So really, PEM is nothing like ischemia-reperfusion injuries.